This resource contains python code to carry out source apportionment of chemicals in river water. Convex optimisation is used to efficiently apportion tracer and pollutant sources from point concentration observations. A minimum working example of the python code and the open-source framework used for the analysis is also provided. Chemical data collected in 2019-2020 along the River Wandle (Thames, UK) were used to test the code and example results are also included. The code assumes conservative mixing and hence is likely to be best suited to assessing chronic sources of pollution (i.e., sources that are temporally invariant, or as near as, during the sampling campaign). Full details about this application can be found at https://doi.org/10.5285/8ae3c419-611d-4bee-ad41-1c9081e79975